1. Field of the Invention
The invention relates to railway rolling stock and comprises a method and apparatus for tramming the wheel and axle assemblies of railway vehicle trucks having separate sideframes supporting and connected by a main frame.
2. The Prior Art
In prior three-piece trucks, which have principally been furnished for freight service, maintaining the trucks in tram has been attempted by interfitting, as closely as practical, opposing surfaces of the sideframes and main transverse frame member, as in the typical spring plankless freight car truck wherein tram maintenance is attempted by initially close-fitting sliding engagement between the bolster and column guide surfaces. Perfect initial tramming of such trucks would require very close tolerance machining of bolster and column guide surfaces and maintenance of perfect tram in such trucks would be difficult because of frictional wear on the opposing surfaces. In trucks of the type in which the main frame is supported, for example, by elastomeric sandwiches, as in F.W. Sinclair patent No. 2981208, extreme precision is also required in the manufacture of the sideframe and bolster interfaces and the sandwich devices and in the assembly of these parts. Manufacturing and assembling these parts to the very close tolerances required for accurate tramming is so costly as to be impractical.